Burner for burning off gas

ABSTRACT

The gas to be burned is delivered through an annular gas inlet into a flared portion at the bottom end of the mixing tube while air is brought in through the open bottom end so that an annular curtain of flame is formed on burning. A means for preventing flashback of the flame is positioned in the upper end of the mixing tube in the form of parallel or concentric tubes. One or more shield tubes are also positioned about the upper end of the mixing tube to permit cooling of the flame by ambient air.

United States Patent 1191 Juricek Apr. 30, 1974 [5 BURNER FOR BURNING OFF GAS 2,167,183 7/1939 Naab et al. 431/351 2,667,156 1/1954 Brown et a], 431/202 [75] l' Wmterthur, 3,354,681 1/1971 Proctor 431/202 Swltzerland 2,888,981 6/1959 Ripple 431 202 ssignee su z oth s td w nt rthur COl'bln Switzerland Primary ExaminerCarroll B. Dority, Jr. [22] Flled: 1972 Attorney, Agent, or Firm-Kenyon & Kenyon Reilly 211 Appl. N0.2 283,402 Carr & Chapm [30] Foreign Application Priority Data [57] I ABSTRACT Aug. 25, 1971 Switzerland 12463/71 The gas to be burned is delivered through an annular gas inlet into a flared portion at the bottom end of the 52 us. (:1 431/346, 431/202, 431/351, mixing tube while air iS brought in through the p 239/423 bottom end so that an annular curtain of flame is [51] Int. Cl. F23d 13/46 formed on burning A means for Preventing flashback [58] Field 6: Search 431/202, 285, 346, 351, of the flame is Positioned in the pp end of the 431/328; 239/424, 423, 416,5 .ing tube in the form of parallel or concentric tubes. One or more shield tubes are also positioned about the 56] Referenees Ci d upper end of the mixing tube to permit cooling of the UNITED STATES PATENTS by amblent 769,568 7 Claims, 2 Drawing Figures 9/1904 Roberts et al. 431/328 MTENTWWR 8Q 1514 BURNER FOR BURNING OFF GAS This invention relates to a burner for burning off gas.

The need to burn off gas arises in many instances, for example, with propane or methane which is transported and stored in tanks at low temperatures in liquid form. Generally, some of the gas, the amount depending on the heat received, always vaporises and cannot always be burnt usefully. I

One object of the invention is to supply adequate air to a gas so that combustion is accompanied by little or no smoke.

It is another object of the invention to provide an ignitable air-gas mixture at all times in a burner.

It is another object of the invention to insure an adequate supply of air to a gas burner at low pressure.

It is another object of the invention to provide for a short flame of burnt gas in a gas burner at relatively large gas volumes.

It is another object of the invention to promote a C- anda effect in the case'of small quantities of gas sup-' plied to a gas burner.

Briefly, the invention provides a burner for burning off a gas which comprises a substantially vertical mixing tube having an open bottom end communicating with the surrounding atmosphere, a gas inlet for introducing a gas into the interior of the mixing tube and means at the upper end of the mixing tube for preventing flashback of a flame. The gas inlet is in the form of an annular gap within the mixing tube and as such affords a simple way of bringing the gas into contact with an adequate supply of air and of mixing the gas and air intimately over a relatively short mixing zone, so that combustion is accompanied by little or no smoke.

ln one embodiment, the bottom end of the mixing tube is outwardly flared and the annular gap is provided adjacent the flared portion. With this construction, the gas/air combustion mixture is always ignitable even if the quantity of gas supplied varies quite widely. The permanent ignitability of the mixture is achieved without using adjusting means so that the burner is not subject to unreliability due to failure of such adjusting means. The construction is such that there is a Coanda effect at the doubly curved surface at the'bottom end of the mixing tube, so that the mixture, even if'present only in small quantities, remains close to the mixing tube wall and the gas is not excessively diluted.

ln one construction, an annular gas supply chamber is provided upstream of the annular gap and is defined on one side by the bottom end of the mixing tube. In addition, the gas supply chamber has a conical inside surface opposite the mixing tube bottom which terminates adjacent the lower surface of the flared portion of the mixing tube to leave the annular gap; the conical surface being approximately tangential to the flared portion. Even if the gauge pressure of the gas is very low, enough air is drawn in for combustion, as the conical interior of the gas supply chamber provides another flared region on the air intake side with the result that the intake pressure drop remains low.

In one embodiment, the means for preventing flashback of the flame is formed of a number of ducts arranged side by side (e.g. like a honeycomb) with their axes parallel to that of the mixing tube. This gives a short flame even if the volume of gas is large, since the gas flowing along the mixing tube surface accumulates at the flashback preventing means and the flame gradually extends toward the burner center as the quantity of gas increases. Preferably, the lower extremities of the ducts adjacent the surface of the mixing tube surface are higher than those of the ducts in the center of the mixing tube. This facilitates the flow of the mixture around the edge of the burner and therefore promotes one result of the Coanda effect, viz. a veil-like exit of the mixture close to the wall in the case of small quantities of gas.

In another embodiment, the means for preventing flashback is formed of concentrically nesting pieces of tubing whose lengths may be the same or may increase with decreasing distance from the center of the mixing tube. Since the flame must not ignite any articles in the vicinity of the burner, the upper end of the mixing tube is provided with at least one shield tube which is open at top and bottom and surrounds and is spaced from the mixing tube. Cold air enters through the open bottom of the shield tube, mixes with the burnt gas and cools the gas to minimize danger to the surroundings.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

, FIG. 1 illustrates a vertical section through a burner according to the invention; and

FIG. 2 illustrates a vertical section through a modified means for preventing flashback of the flame according to the invention. I

Referring to FIG. 1, a burner 1 has a vertically disposed mixing tube 2 whose bottom end 3 flares outwardly like a trumpet. A- means 4 for preventing flashback ofa flame generated in the burner l is located at the top end of the mixing tube 2. This means 4 includes ducts arranged like a honeycomb and having axes parallel to the mixing tube 2. The upper end of the mixing tube 2 is surrounded by two shield tubes 5, 6 axially offset relative to one another. Both shields tubes 5, 6 are open at top and bottom and are arranged so that one shield tube 5 surrounds the upper end of the mixing tube 2 in spaced relation while the other shield tube 6 surrounds the shield tube 5 in spaced relation.

The bottom trumpet-like end 3 of the mixing tube 5 ends in a radial flange 7 to which an annular casing 8 is fixed as by screws 9. In this embodiment, four lines 10 (of which only three are visible) are connected to the casing 8 and to one or more tanks (not shown) containing gas which is liquid at low temperatures (for example methane or propane). The annular casing 8 has a conical internal wall 11 whose upper end 12 ends near the trumpet-like flared portion 3 and is approximately tangential to the curvature of this portion as shown. An annular gap 13 is left clear between the end 12 of the conical wall and the flared portion 3. The annular casing 8 and flange 7 of the mixing tube 2 cooperate to form a gas supply chamber 14 upstream of the annular gap 13. The space within the conical wall 11 connects the bottom end of the mixing tube 2 to the atmosphere.

During operation of the burner l, varporised liquid gas enters the gas supply chamber 14 through the line 10 and exits through the annular gap 13 into the bottom end of the mixing tube 2. Here the gas mixes with the air entering from below (as indicated by arrows 16). Because of the trumpet-like shape of the mixing tube 2, mixing takes place close to the wall of the tube 2. The mixture then flows upwards, also close to the wall of the mixing tube. After flowing through the peripheral ducts in the flashback preventing means 4, the air/gas mixture is ignited by a suitable ignition means such as a pilot burner or incandescent igniting means (now shown) above the flashback preventing means 4 and burns as a veil-like flame 15. Cold air is sucked in through the lower openings of the shield tube 5 and 6 and mixed with the burnt gas, so that the gas leaving the shield tube 6 is cooled enough not to ignite any articles in the vicinity of the burner.

If the quantities of gas are small, the veil-like flame is shaped like a thin tube, whose wall thickness increases with the quantity of gas as the ducts nearer the center of the mixing tube 2 begin to receive gas.

Referring to FIG. 2, in order to assist this above effect, the flashback preventing means 4' can be constructed so that the ducts near the wall of the mixing tube 2 are shorter than those in the center of the mixing tube 2 with all the ducts extending downwardly from a common horizontal plane. This facilitates the passage of the mixture through the ducts near the wall of the tube.

Alternatively, instead of having a honeycomb arrangement of ducts, the flashback preventing means may comprise concentrically nesting pieces of tubing (now shown) whose lengths may be the same or may increase towards the center of the mixing tube.

What is claimed is:

1. A burner for burning off gas comprising a substantially vertical mixing tube having an open bottom end communicating with a surrounding atmosphere and a curved outwardly flared portion at said bottom end;

a fuel gas inlet disposed near said bottom end of said tube in communication with a source of fuel gas and adjacent said flared portion for introducing a gas into said mixing tube in an annular pattern;

means at an upper end of said mixing tube for preventing flashback of a flame generated by burning of the gas passing through said mixing tube; and

an annular gas supply chamber upstream of and in communication with said gas inlet, said mixing tube defining a side of said chamber, and said chamber having a frusto conical wall surface opposite said mixing tube extending approximately tangentially towards and terminating adjacent a lower surface of said flared portion of said mixing tube to define said gas inlet.

2. A burner for burning off gas comprising a substantially vertical mixing tube having an open bottom end communicating with a surrounding atmosphere;

a gas inlet disposed near said bottom end of said tube for introducing a gas into said mixing tube in an annular pattern; and

means at an upper end of said mixing tube for preventing flashback of a flame generated by burning of the gas passing through said mixing tube, said means including a plurality of ducts arranged in side by side relation with axes parallel to a longitudinal axis of said mixing tube, said ducts adjacent the peripheral surface of said mixing tube having lower extremities disposed in a higher horizontal plane than the lower extremities of said ducts in the center of said mixing tube.

3. A burner as set forth in claim 1 wherein said means includes a plurality of ducts arranged in side by side relation, said ducts extending downwardly from a common horizontal plane having axes parallel to a longitudinal axis of said mixing tube, said ducts adjacent the wall of said mixing tube being shorter than the ducts in the center of said mixing tube.

4. A burner as set forth in claim 1 further comprising at least one shield tube having an open top and open bottom disposed in spaced surrounding relation about said upper end of said mixing tube.

5. A burner as set forth in claim 1 further comprising an ignition means above said means for preventing flashback.

6. A burner as set forth in claim 5 where said ignition means is an incandescent lighting means.

7. A burner as set forth in claim 5 where said ignition means is a pilot burner.

* a a a a 

1. A burner for burning off gas comprising a substantially vertical mixing tube having an open bottom end communicating with a surrounding atmosphere and a curved outwardly flared portion at said bottom end; a fuel gas inlet disposed near said bottom end of said tube in communication with a source of fuel gas and adjacent said flared portion for introducing a gas into said mixing tube in an annular pattern; means at an upper end of said mixing tube for preventing flashback of a flame generated by burning of the gas passing through said mixing tube; and an annular gas supply chamber upstream of and in communication with said gas inlet, said mixing tube defining a side of said chamber, and said chamber having a frusto conical wall surface opposite said mixing tube extending approximately tangentially towards and terminating adjacent a lower surface of said flared portion of said mixing tube to define said gas inlet.
 2. A burner for burning off gas comprising a substantially vertical mixing tube having an open bottom end communicating with a surrounding atmosphere; a gas inlet disposed near said bottom end of said tube for introducing a gas into said mixing tube in an annular pattern; and means at an upper end of said mixing tube for preventing flashback of a flame generated by burning of the gas passing through said mixing tube, said means including a plurality of ducts arranged in side by side relation with axes parallel to a longitudinal axis of said mixing tube, said ducts adjacent the peripheral surface of said mixing tube having lower extremities disposed in a higher horizontal plane than the lower extremities of said ducts in the center of said mixing tube.
 3. A burner as set forth in claim 1 wherein said means includes a plurality of ducts arranged in side by side relation, said ducts extending downwardly from a common horizontal plane having axes parallel to a longitudinal axis of said mixing tube, said ducts adjacent the wall of said mixing tube being shorter than the ducts in the center of said mixing tube.
 4. A burner as set forth in claim 1 further comprising at least one shield tube having an open top and open bottom disposed in spaced surrounding relation about said upper end of said mixing tube.
 5. A burner as set forth in claim 1 further comprising an ignition means above said means for preventing flashback.
 6. A burner as set forth in claim 5 where said ignition means is an incandescent lighting means.
 7. A burner as set forth in claim 5 where said Ignition means is a pilot burner. 